The present invention relates to an ultrasonic device for the measurement of the delivery of a fluid in a conduit.
In particular, the present invention relates to a device based on the principle of the detection of the deviation of the phase difference provided by two ultrasonic signals which are transmitted and received between respective electroacoustic transducers in two opposing directions, the transducers being disposed inside a conduit in which fluid flows.
More particularly, the present invention relates to a device of the above-mentioned type and advantageously usable in the automotive field for the measurement of the air delivery in direct injection engines, for which it has been observed that the mass delivery values are typically in the range between 0 and 150 grams/second and are subject to very sudden changes.
As is known, in the measuring devices of the above-mentioned type, the electroacoustic transducers are suitably arranged in the wall of a pipe delimiting the conduit and along an axis which is obliquely disposed in relation to the axis of the conduit itself, so that the signals transmitted and received are functions of the modulus of the speeds of the fluid in the conduit and the angle that the straight line connecting the transducers makes with the axis of the conduit. It has been observed, however, that the information delivered by such devices displays good correlation between phase changes and air mass delivery only in a situation of slow steady flow (e.g., 20 g/sec), while they are less reliable when the flow inside the conduit is turbulent, that is, when the radial components of the vector repsesenting the fluid speed become significant in relation to the axial components. Unfortunately in the automotive applications the degree of turbulence of the air passing through the measuring conduit is somewhat high, whereupon, at present, none of the devices of the above-mentioned type are suited to carry out delivery measurements reliably. On the other hand, the use of mechanical devices in these cases is absolutely inexpedient, both due to adverse effect of their inertia on the response speed, and because, as a consequence of their structure comprising moving mechanical members, they are more liable to failures due to wear.